AFP is the most sensitive and specific tumor marker for primary liver cancer. Therefore, the detection of AFP concentration in blood has special clinical significance for the diagnosis of primary liver cancer. I. Fetal period, elevated AFP in maternal blood: may be due to intrauterine fetal death, genetic defects, neural tube malformation, anencephaly, spina bifida and other conditions. In early childhood, elevated AFP in the blood of newborns may be due to heart failure, liver stasis, bile duct atresia, hepatitis, etc. Elevated AFP in the blood of children may be due to hepatocellular carcinoma, hepatoblastoma, gonadal teratoblastoma, hepatitis, etc. Elevated AFP in adult blood: (i) When hepatocellular carcinoma occurs, the gene for synthesizing AFP in the cells is reactivated, so that the cells that have lost the synthesis function start to synthesize AFP again, resulting in a significant increase in the level of AFP in the patient’s blood. In primary hepatocellular carcinoma, 80-90% of patients have significantly higher AFP content in serum, and 77% have AFP>500ug/L. About 18% of hepatocellular carcinoma patients do not have elevated AFP, which may be due to the fact that the differentiation of hepatocytes in such carcinoma is close to normal or the degree of degeneration and necrosis is severe, and the amount of AFP synthesized in cancer tissue is low due to the excessive connective tissue components. (ii) Increased AFP content in the serum of patients with embryonal tumors of gonads, such as testicular cancer, ovarian cancer, teratoma, etc.; (iii) AFP content of other malignant tumors, such as pancreatic cancer and bile duct cancer, may also be increased; (iv) AFP content of patients with viral hepatitis and cirrhosis has increased to different degrees, and gradually decreases as the condition improves; (v) AFP content in the serum of women begins to increase after the third month of pregnancy, and reaches a peak at 7-8 months. (v) AFP levels in the serum of women begin to increase after the third trimester of pregnancy and reach a peak at 7-8 months, but are generally below 400ug/L and return to normal three weeks after delivery.